An electromechanical system in one example measures a parameter. The electromechanical system may comprise a micro-electromechanical system (“MEMS”) accelerometer or gyroscope that measures the parameter. For example, the accelerometer measures an acceleration and the gyroscope measures a rotation. The accelerometer in one example comprises a proofmass sensor component supported at a flexure point by a frame. The flexure point is compliant to allow movement of the proofmass upon occurrence of an acceleration. Pickoff and processing components measure and translate the movement of the proofmass into a direction and magnitude of the acceleration.
A proofmass is employable to sense an acceleration in one direction. For a more complete analysis of the acceleration, three proofmasses are used in combination. For example, a first proofmass is oriented to sense acceleration along a first direction (e.g., x-axis), a second proofmass is oriented to sense acceleration along a second direction (e.g., y-axis), and a third proofmass is oriented to sense acceleration along a third direction (e.g., z-axis). The three directions in one example are orthogonal. The three proofmasses are arranged in a triad to determine an accurate direction and magnitude of the acceleration.
In one example, the first proofmass is attached to a first face of a cube, the second proofmass is attached to a second face of the cube, and the third proofmass is attached to a third face of the cube. Sensitive axes (i.e., input axes) of the proofmasses are orthogonal to the mounting surface of the cube. Thus, the cube with the three proofmasses is employable to measure acceleration in any direction by combining the measurement from the three proofmasses. As one shortcoming, the size of the accelerometer is large due to the requirement to orient three proofmasses in three different planes. As another shortcoming, it is costly to interconnect the three proofmasses in the three different planes. As yet another example, since the three proofmasses are oriented in the three different planes, the proofmasses may not have limit stops to prevent damage during high accelerations in some directions.
In another example, the three proofmasses are coplanar. Flexure components that connect the proofmass with the frame may be too compliant allowing excessive out of plane movement. As one shortcoming, the excessive out of plane movement causes non-linearity performance errors in the acceleration measurement. The sensitive axes of the three proofmasses in one example do not intersect at a common point. The processing component that calculates the acceleration must employ compensation algorithms that account for the fact that the sensitive axes of the three proofmasses do not intersect at a common point. As another shortcoming, the compensation algorithms complicate the acceleration calculation process.
Thus, a need exists for an electromechanical system that comprises three coplanar proofmasses employable to sense acceleration along three axes. A further need exists for the electromechanical system to prevent non-linearity performance errors in acceleration measurement. Yet a further need exists for the electromechanical system to promote a reduction in computational complexity of compensation algorithms that calculate the acceleration sensed by the electromechanical system.